FHR baseline is not only an important indicator which reflects the development state of a fetal central nervous system and indicates fetal safety, but also a middle parameter which shall firstly be determined by the medical staff when they analyze fetal monitoring (hereinafter referred to as fetal monitoring) diagram. Generally, the FHR baseline will gradually decrease with increasing gestational weeks, and the normal range is 110 bpm˜160 bpm. The medical staff shall attach importance to too high FHR baseline or too low FHR baseline. They shall find out the cause of the abnormality immediately, determine whether this exception has clinical significance, and provide the basis for the intervention measures. For example, during pregnancy, if the FHR baseline drops and is below 100 bpm, they shall consider that there may be congenital heart disease. However, during childbirth, FHR baseline abnormalities are warning signs of fetal distress. At this time, they shall find out the reason for the exception as soon as possible and take certain intervention measures to eliminate the abnormalities, thus ensuring safety of the fetus. Meanwhile, the FHR baseline is also the basis for the medical staff to determine other fetal intermediate physiological parameters, such as acceleration, deceleration, mutation, etc. These intermediate parameters may be determined only on the basis of the determination of the FHR baseline.
Currently, a clinical method for calculating the FHR baseline is mainly an average method. Effective FHR data of 10 minutes or more is obtained through a fetal monitoring module. After the data are processed simply, their average values are calculated. Furthermore, a straight line is drawn on a fetal monitoring drawing based on the average values and taken as the FHR baseline. However, this method is only suitable for conditions where the FHR-curve is relatively stable and there is no change in FHR baseline. Actually, due to fetal movement, uterine contractions and the impacts of various external stimuli, the FHR is accelerated and decelerated as well as has other regular changes. As the average method may not avoid the impact on the calculation results caused by these changes, the calculated FHR baseline is always deviated from actual values. Meanwhile, as the FHR baseline may vary with the changes of fetal wake cycle, as to the average method, only one value may be obtained from all of the data, and hence the changes of the FHR baseline may not be identified. Therefore, if the fetus is under different states, the FHR baseline may vary. As the FHR baseline identification method in the prior art not only cannot avoid the impact on the results caused by the FHR regular changes but also cannot vary with the different states of the fetus, the calculated FHR baseline deviates from the actual values, and regular changes of the FHR cannot be displayed in fetal monitoring diagrams. In a word, as the average method cannot process the interference data, the calculated FHR baseline is inaccurate and unstable.